Clutch assembly



Jan. 27, 1959 I J. w. PALM 2,870,893

CLUTCH ASSEMBLY Original Filed May 12, 1951 2 Sheets-Sheet 1 kfames ZZZ Palm Jan. 27, 1959 V w. PALM 2,

CLUTCH ASSEMBLY Original Filed May 12, 1951 2 Sheets-Sheet 2 fnz/enZZr" James Z0. falm plates CLUTCH ASSEMBLY James W. lfalm, Rockford, IlL, assignor to Borg-Warner Corporation, Chicago, 11]., a corporation of Illinois Original application May 12, 1951, Serial No. 226,069,

new Patent No. 2,742,129, dated April 17, 1956. Digglsegsalnd this application March 1, 1956, Serial No.

3 Claims. (Cl. 192-413) The present improvements relate generally to clutches and more particularly to clutches which are adapted for heavy duty where severe service is required.

This application is a division of my copending application, Serial No. 226,069 filed May 12, 1951, for Clutch Assembly now U. S. Patent N0.2,742,129 dated April .has been found. that some of the parts are damaged to .such an extent that theyrequire replacement which causes delay in completing the taskbeing performed. When overcenter engaging and disengaging mechanism isemployed in these clutch assemblies, some of the component parts of the overcenter mechanism when rotating at high idling speeds and the clutch has been disengaged these overcenter parts frequently respond to centrifugal forces with the result that these parts tend to effect unintentional engagement of the clutch driving and driven ,It is desirable in clutches o f this character to provide yieldable means between the pressure applying mechanism or toggle devices and the shiftable pressureplate so as to exert spring force against these toggle devices to hold them in overcenter position when the clutch has been engaged. The yieldable means preferably takes the 3 form of a spring bar locatedjbetween the pressure plate and the oyercenter toggle. mechanism, so, that, when the friction surfaces of the clutch driving and driven members wear,,the pressure plate is permittedto followup with a sufiicient amount of 1 pressure supplied by the spring,bar, and this Pressure, in turn, is applied to the driyen member to' maintain the required amount of its que. .B rcas u .Q s f nct o n f t sbar,

di s t n ..'rs ssl of sp l tsh. se e .rsduced to a -minimum, There are several spring bars -on the pressure plate, so that the follow-up travel of the pressure plate, which is produced by thesespring bars, is approximately equal to the deflected length oftlie spring bars from their preloaded positions to their fully .deflected positions. The spring means in the present assembly also performs the function of providing a yieldable force between the pressure. plate and its shifting 'means for effecting a cushioned engagement of the] clutch drive and driven members. H

The present improvements have been carefully designed and have been successful in preventing the abovedescribed objectionable. conditions arising in a clutch assembly which is installed in a motor ,driven vehicle where severe se'rviceis encountered while performing new o ice Fatented Jan. 27, 1959 operating mechanism from unintentionally shifting at high idling speed from a position in which the clutch is disengaged to a position where said mechanism causes accidental clutch engagement; and (3) the employment of yieldable spring means, preferably in the form of a spring bar, which is acted on by the toggle devices for cushioning the engaging movement of the pressure plate against the clutch driven plate and also to. assist in holding the toggle devices in overcenter positions while the clutch is engaged.

An object contemplated by the present improvements is to provide definite means on certain of the rotatable members of the clutch assembly for creating the flow of air currents which are drawn into the assembly through an axial opening in the backplate or housing and then be directed between said backplate and the shiftable pressure plate and other parts in radially outward paths so that the coolant air, after impinging upon the clutch parts, is discharged through an annular row of apertures in the backplate or housing. Specifically, this object is attained by providing a plurality of fins extending in generally radialdirections on the inner'surface of the backplate or housing of the assembly, or providing similar fins on the rear surface of the clutch pressure plate.

Another object contemplated bythe present improvements resides in providing automatically operable means which are responsive to centrifugal forces, created at high idling speeds of the assembly when the clutch has been disengaged by the overcenterdevices, said means being effective to overbalance a tendency of said overcenter devices, due to centrifugal forces acting thereon,

to move out of a clutch disengaged position, into a posiis responsive to centrifugal forces to counteract the tendency of the toggle device to leave its clutch disengaged position.

The further object contemplated by the present mechanism resides in mounting a leaf spring bar at its end regions on supports on the rear face of the pressure plate and forcibly tensioning or bowing the midregion of this spring bar toward the pressure plate by means of a tensioning device which will lengthen the bar between its end supports. In this connection, the toggle devices are arranged to engage the. spring bar at its bowed region so that the bar will be further elongated between its supports when the clutch driving and driven members are engaged. The yieldable action of the spring bar is also effective to maintain the toggle device in its overcenter position when the clutch parts have been drivingly engaged.

Additional objects, aims, and advantages of the improvements contemplated herein will be apparent to persons skilled in the art after the construction and operation of the present clutch assembly is understood from. the

within description. It is preferred to accomplish the foreamoeba '3 substantially the manner hereinafter fully described and as more particularly pointed out in the claims, reference being made to the accompanying drawings which form a part of this specification.

In the drawings: Fig. l is vertical elevation showing a rear viewof an overcenter heavy'duty clutch assemblyexemplifying the features contemplated by present improvements;

Fig. 2 is a transverse vertical section ofthe structure shown in Fig. l, the view being taken along the plane of line 2--2 thereon;

Fig. 3 is a sectional view of a fragmentary portion of the clutch taken along the plane of line 33 on Fig. 1;

Fig. 4 is a schematic view showing details of the bowed spring bar and its manner of operation, the view being taken along the plane of line 4-4 on Fig. 1;

Fig. 5 is a fragmentary detail of the overcenter or toggle device in clutch disengaged position with respect to the pressureplateand the spring bar;

Fig. 6 shows a modified arrangement for creating coolant air currents.

The drawings are to'beunderstood as being more or less of a diagrammatic character'for the purpose of disclosing a typical or preferred form of the improvements contemplated herein, and in these drawings like reference characters identify the same parts in the different views.

Figs. land 2 of the drawings exemplify a typical clutch assembly of the heavy duty type and show the present improvements incorporated therein. Inthese views, the flywheel assembly A comprises a flywheel 10 which-is anchored in any suitable manner to the adjacent end of an engine drive shaft or crank shaft 11, and alongside the rear face. of this flywheel there is a driven friction disc or plate :12 having a splined hub, 13 for mounting the same for axial *movementalong the adjacent'spline'd portion of the driven shaft 14. This driven -shaft, as seen in'-Fig. 32, has a-reduced end portion 14a :which-is piloted-in antifriction bearings 15 carried by'the'fiywheel, or the driveshaft, =as1may be desired. The friction disc or plate'12 is adapted to be drivingly engaged against the flywheel face through the medium of an annular pressure plate 16that is shifted axially by :an actuating assembly B which yieldahly holds the pressure plate in clutchengag'ed position against saidfriction disc. "The actuating assembly B has one portion in cooperative association with a back-plate or housing assembly C, and it has a second portion which is operably connected to a shift hearing or thrust collar assembly D, the latter assembly beingselectively moved manually in forward or rearward directions along the driven shaft 14 for the purpose of eflecting the respective engagement or disengagement of the driven friction disc or plate 12 between the flywheel and the pressure plate at'the option of the operator or driverof the tractor or other vehicle.

The backplate assembly C preferably takes the form of a housing 17 having an irregular-contour in cross section with an outer-peripheral flange '18 which is secured by cap screws 19 to an annular flange -20-extending rearwardly *from the outer periphery of the flywheel.

'The flywheel flange '20 provides an annular recess 10a in therear face of the-flywheel so'that thefrictionplate and pressure plate may be positioned in this recess rarwardly of the backplate or housing and thereby reduce the overall axial dimension of the clutch assembly. The pressure plate whats a driving connection with the backplate or housing 17 through the instrumentalityof rearward or axially extending lugs 21 which are engaged in recesses 22 in adjacent regions of thebackplate, thus permitting the pressure plate, housing. and flywheel'to rotate in unison.

At the central region of thehousing, there is an annular flange 23 of generally cylindrical shape which extends axially rearwardly to define a large axial opening 24.

The cylindrical flange 23 surrounds the'drivenshafft 14 and is spaced a considerable distance radially "from the "in Fig. l.

saidshaft .to define an inlet. opening for the ingress of extraneous coolant air intothe housing when the clutch assembly is in rotation. For the purpose of drawing air into the housing through the opening 24 to impinge upon the clutch members, suitable fins 25 are provided which project axially away from the pressure plate from the inner surface of the housing, and said tins are of an elongate character and extend in generally radial directions on the housing between the axial opening 24 and the annular flange 18 at the outer periphery of the housing. .Also, as shown in Fig. 6, fins 25a may be positioned upon the rear surface of the pressure plate which rotates with the backplateor housing, and will thus draw extraneous coolant air into the clutch assembly. Between the axial opening 24 and the outer pcripheral flange 18, the housing has therein a plurality of openings 26, which are arranged in an annular row and are each elongated in a circumferential direction as seen This annular row of apertures 26, define egress or outlet means for discharging the'coolant air after it has circulated within the housing and has impinged upon the clutch members in which heat has been generated during operation of the clutch. It will be understood that the coolant air is forcibly drawn into the clutch assembly by means of the fins which function as rotating fan blades, with the result that the temperature of the clutch parts is materially reduced and prevented from becoming overheated, particularly when the clutch is disengaged and may be idling at high speeds.

In addition to the driving lug connection between the pressure plate 16 and the housing or backplate, there are spring reaction connections between these members, each of which comprises a bolt 27 having its head 28 seated in recess 29 on the front face of the pressure plate and has its shank extended through the pressure plate and the housing. l8xas'sho'wn iniFig. 3. A: coiled expansion spring'30 surrounds the outer rearward portion of the bolt with one 'end' engaged with the rear "surface" of "the 'housing and the otherendengaged with an adjusting nut 31 whereby the spring-isheld under tension. Thus it is apparent that the spring30 assists in drawing the pressure plate away from the friction disc when the driving and driven members of the clutch have-disengaged.

The actuating assemblies B operate to move the pressure plate in one axial direction into contactwith'the standing position and are pivotally connected at their lower regions by a pin 33 to an annular boss -34formed "as apart of the shift bearing'or thrust'collar assembly D. Fig. "2, shows the assembly D as comprising an axially elongate sleeve '35 on driven sha'ft .14 with an annular .boss 34 at its 'forward end and having a 'collar '36'surrounding its rear reg'ionwithantifriction bearings 37 interposed between'said sleeve "and collar. The usual shift fork (not shown) engages the collar 36 formoving thethrust bearing assembly'D longitudinallyon'the'driven shaft'14 to operate the'toggle of the clutch actuating assembly D. The outer surface of the "annular axial flange 23 of the housing is threaded 'to receivea take-up ring '38 of L-shape in cross section which is similarly threaded on the inner surface of 'its axial flange, whereby thering 38 may be rotatably adjusted on its support. Mounted in the angle formed by the L-shape flanges of the ring, there is an annulus 39 which is arranged with one face abutting the radial flange of the ring and is held in place by a spring snap ring device which contacts the opposite face of said annulus. The secondmemberof the overcenter toggle comprises an arm 41'extendingin a generally horizontal directioncwithlits rearward end coupled to the adjacent end of :the Siamese links 32 by p a pin 42, and the forward end of link 41 .is pivotally connected to the annulus by a pin 43extending between a pair of ears 44 on the annulus. A second arm 45 extends forwardly of the pin 43 towards the pressure plate 16 and is provided with a weight 46 on its free end so that the arm 45 is responsive to centrifugal forces created by the rotation of the clutch assembly.

In operation, when the shift collar assembly Dis moved to the right from the position shown in Fig. 2, the actuating assembly assumes the position shown in Fig. 5 so that the toggle, comprising links 32 and .arm 41, assume a somewhat flattened position and the clutch is disengaged. In the event the clutch maybe rotating at high idling speeds, the knuckle portion of the toggle device at the pin 42 has the tendency to move radially outward to a. position where the arrangement is likely to effect unintentional clutch engagement or at least move the clutch members closeenough to each'other as to create a drag on the friction members. This tendency of the toggle to unintentionally engage the clutch parts is definitely avoided by reason of the fact that the weighted arm 45 overbalances the centrifugal forces which have been exerted onthe toggle. l

The connection between the pressure plate 16 and the toggle assembly B preferably takes the form of a cam member 47 on the hub region of the arm .41 adjacent the pivot pin 43 and is arranged with its toe projecting toward the pressure plate. In view of the fact that heavy duty friction discs are ofa simplified type without cushioning means between the facings andjthe intermediate plate thereof, it is desirable, though not essential, to ,provtde means for cushioning clutch packing pressure .when the clutch is being engaged. In the present arrangement, a cushioningeffect is acquired by providing spring-meansbetween the pressure plate and the toggle, said means being preferably in the form of a spring metal bar 48. This spring bar 48, as shown on Fig. 1, is of elongate form and is mounted at its end regions on supports 49 on the rear of the pressure plate so that I said spring bar extends in a direction generally transverse to the plane of the toggle assembly B. Suitable clips 50 hold the bar on its supports and said bar is forcibly held in a bowed state between its ends by means of a heavy retainer member or bracket member 51, which is anchored to the pressure plate by a cap screw 52. The supports 49 at the ends of the spring bars 48 are located on the mean radius of the rear face of the pressure plate, which is between the inner and outer peripheries of said plate, so that even pressure is produced on the friction surfaces of the driven disc member. Thus distorted or uneven conditions are prevented on the surfaces when there is wear on the driving and driven members of the assembly. The spring bars are deflected to stops 49a on the rear surface of the pressure plate intermediate the supports 49, and these stops allow the clutch to be adjusted beyond its rated torque capacity without injury to the spring bars. After an overload of pressure, that has been applied to the pressure plate, is decreased and is equal to the pressure produced by the fully deflected spring bars, the pressure of the fully deflected spring bars is applied to the driven disc member. The initial amount of deflection of the spring bar is not sufficient to produce any appreciable amount of pressure required to operate the clutch to its torque capacity. Therefore, the spring bar is preloaded or trapped at a specific height, and it is from this preloaded height position to the fully deflected position of the spring bar that sufficient pressure is produced to operate the clutch at its specified torque. The trapped or preloaded condition of the spring bar eliminates the requirement of having a larger releasesleeve travel to obtain ample pressure plate release travel.

The bowed midregion of the spring bar 48 is'adapted to be engaged by the toe ofcam 47 duringthe operation of engaging the clutch members. When the thrust collar is movedin a forward direction (to the .left in Fig. 2) the cam 47 will increase the bow of the spring bar 48 and thereby the spring bar is lengthened between its supports. This is schematically shown in detail in Fig. 4 wherein it is to be noted that the full lines show the spring bar 48in its normal bowed state, and the dotted lines show bowed effect resulting from the engagement of the cam 47 with the midregion of said bar. When the clutch is in engaged position, the toggle is in overcenter position as in Fig. 2, so that the spring tension of the bar 48 is exerted against the cam 47 and tends to swing the knuckle portion of the toggle in a downward direction to effectively maintain the toggle against any flattening movement thereof. In other words,

the spring bar 48 is capable of performing the abovedescribed dual functions. Furthermore, when the toggle assembly B is moved towards either clutch engaged or disengaged position, the toggle assembly will pass from one side to the other of the overcenter position with a snap action, and this overcenter snapping action is effectively cushioned by the spring bar. a As previously explained, the take-up ring 38 is screwe on the exterior surface of the flange 23, and since the toggle arrangement is carried by this take-up ring through the medium of the annulus 39, said ring may be rotated in one direction or the other to bodily move theassembly toward or away from the pressure plate 16 as desired.

The take-up ring is locked in its selected positions by means of a latch assembly 53 that is hingedly mounted between ears b on a rear portion of the housing by means of a pivot 54 and is provided with an arm 55 projecting radially inward to engage in one of the notches 56 made in the edge or outer periphery of the take-up ring 38. A spring 57 of approximately U-shape is citedtive to hold the latch device in its engaged position with respect to the notches 56.

From the foregoing description it is apparent that the arms 41 and 45 define a rock lever or bell-crank member which is fulcrumed intermediate its ends on the pivot pin 43, and also that the cam member 47 provides What maybe termed a third or auxiliary arm of the bellcrank. When cam 47 acts upon the spring bar 48, there is a cushioning of the force which is being applied to the pressure plate by the toggle device during movement of the clutch members into clutch engaged positions. This spring bar is effective to assist in holding the toggle members in overcenter positions during clutch engagement. Also certain portions of the clutch assembly have air circulating fins which produce air currents to reduce the temperature of the working parts of the clutch.

While the present structure has been described in detail in a typical or preferred form or embodiment, it will be apparent to persons skilled in the art, after understanding the construction and operation of the improvements contemplated herein that various changes and modifications thereof may be made without departing from the spirit or scope thereof. It is contemplated in the appended claims to cover all such changes and modifications.

What is claimed is:

1. A friction clutch assembly of the heavy duty type which is subject to heating during operation, comprising driving members and a driven member, one of said driving members being movable axially with respect to the other driving member to frictionally engage said driven member therebetween; means defining a back plate attached to one of said driving members and arranged rearward thereof and said other members, means defining an axial opening of substantial dimensions in the center of said back plate, said back plate also having an annular row of circumferentially spaced apertures extending axially therethrough communicating the front and rear surfaces thereof between its outer periphery and said axial opening adapted to provide air channels; and a plurality of fins on-"the "rear'surface of said back'plate projecting axially'awayfrom said driving members and extending radially betweensaid-central axial opening and the outer periphery of said'back'plate jfora distance substantially equal to the spacing between "said central opening and said outer periphery effective during operation of the clutch assembly: to draw'extraneous coolant air into said clutch assembly through said central axial opening-to impinge upon and cool saidtdriving and driven members, and to discharge :said coolant air through said annular row of apertures.

- 2. ,A friction clutch assembly of the heavy duty type which is subject to heating during operation, comprising driving members'and adriven'membenpne of said driving members beingmovable axially with respect to the other driving member to frictionally engage said driven member therebetween; a plurality 'of generally radial fins on said movable driving member; an annular housing carried by one of'said drivingmembers andenclosing the other driving member andsaid driven member, said housing having a generally radial back wall withan axial opening centrally disposed therein of substantial dimensions, and also having an annular row of circumferentially spaced apertures between its outer peripheral portion and said axial-opening; and a plurality of fins extending in generally radial directions on the rear surface of said housing back wall projecting axially away from said driving members and extending radially between said centrally disposed opening and the outer periphery of said back plate, said driving member fins and said housing fins being ,eifective to draw extraneous coolant air .into said housing through said axial opening to impinge upon and cool'said driven and driving members, andto discharge said coolant air'through said annular row of apertures.

3. A friction clutch assembly .of the "heavy duty type which is subject to heating during operation, comprising 8 axially spaced driving members, and a driven member between said driving members, one oflsaid driving mem# bers being movable axially with respectto the-other driving member to f'rictiona'lly engage said driven member therebe'tween; means defining a back plate carried :by oneof :sa-iddriving members and spaced rearwardlyof said-members, 'said back 'platehaving an axial opening centrally located therein of substantial dimensions and also an annular row of circumferentially spaced apertures adjacent its outer periphery; overcenter clutch'operating means pivotally mounted on said back plate and extending through-said aperturesythe inner portions of said overcenter means being arranged for engagement with'said axially movable driving member;-pressure exerting means rearward -of*said backplate andpivotally connected to the outer portion of said overcenter means; a plurality of fins extending in generally radial directions on said axially movable driving member and said back plate, said back plate fins projecting axially away from said driving members *an'dexten'ding radially between said centrally disposed opening and the outer periphery of said backplate, said 'finsb'eing efiective to draw extraneous coolant air into said housing through said axial opening past said overcenter-means to impinge upon and cool said driving and driven membersand to discharge said coolantair through saidannular row of apertures.

R'ferencesCitetl in'the file of'thispatent UNITED STATES PATENTS 1,515,401 "Norris -Nov. 11, 1924 1,707,843 Byerlein 'Apr. 2, 1929 1,731,416 Gurney Oct. 15, 1929 1,767,309 Ricardo June 24, .1930 2,060,773 'Pearmain Nov. 10, 1936 $2,089,786 *Eason Aug. 10, 1937 '-2.',241,241 Clouse May '6, 1941 

